This workshop/conference will focus on the role in carcinogenesis and mutation of cyclic nucleic acid adducts produced by vinyl halides, alkyl carbamates, mono- and bi-functional aldehydes, epoxides, halonitrosoureas and related compounds. Although the chemicals to be discussed include known or suspected human carcinogens (vinyl chloride, acrylonitrite, cyclophosphamide), little is known of their biological mechanism of action. Even less is known about other animal carcinogens of these classes to which humans are exposed. All the chemicals to be discussed have one thing in common. They, or their metabolites, form an additional ring on one or more nucleotides, or they have a similar chemical structure which makes it likely that such adducts are also formed. The proposed conference will bring together American, European and Japanese experts in metabolism, chemistry, toxicity, mutagenesis, carcinogenesis and repair. Five sessions include (1) the occurrence, epidemiology, carcinogenesis and structure-activity relationships; (2) metabolism to cover species, organ and cell-specificity of activation reactions; (3) chemistry and formation of macromolecular binding adducts; and (4) the biological consequences of these cyclic nucleic acid or other macromolecular adducts in relation to toxicity, mutagenicity, repair and carcinogenicity. The impact of such an international and multidisciplinary conference in a field covered by only a few investigators should codify what is known and, more importantly, draw attention to future research needs of classes of carcinogens not included in the many meetings dealing with nitrosamines and various aromatic carcinogens.